Organic light-emitting diode (oled) display and method of manufacturing the same

ABSTRACT

An organic light-emitting diode (OLED) display and method of manufacturing the same are disclosed. In one aspect, the OLED display includes a substrate which includes non-emission regions and emission regions, a first electrode which is formed on each of the emission regions of the substrate, an organic light-emitting layer which is formed on the first electrode, a second electrode which is formed on the organic light-emitting layer and the substrate and a passivation layer which is formed on the second electrode. The passivation layer includes a first passivation layer which substantially overlaps the organic light-emitting layer and a second passivation layer which does not overlap the organic light-emitting layer, wherein the refractive index of the first passivation layer is higher than the refractive index of the second passivation layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No.10-2013-0077830 filed on Jul. 3, 2013 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field

The described technology generally relates to a display device and amethod of manufacturing the same, and more particularly, to an organiclight-emitting diode (OLED) display and a method of manufacturing thesame.

2. Description of the Related Technology

The development of information and communications technology and thediversity of the information creates a continuously increasing demandfor display devices. Display devices include cathode ray tubes (CRTs)and liquid crystal displays (LCDs). In particular, organiclight-emitting diode (OLED) displays are unique due to their exceptionalcharacteristics.

Unlike LCDs, OLED displays do not require a light source since OLEDs areself-emissive. Therefore, OLED displays generally have reduced thicknessand weight. Additionally, OLED displays have a wide viewing angle, lowpower consumption, high luminance and high response speed. Due to theseadvantages, OLED displays are being actively developed asnext-generation displays.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

One inventive aspect is an organic light-emitting diode (OLED) display(hereinafter to be interchangeably used with “OLED display device”)which includes a filler structure having improved light-emissionefficiency.

Another aspect is a method of manufacturing an OLED display whichincludes a filler structure having improved light-emission efficiency.

Another aspect is an OLED display comprising a substrate which comprisesnon-emission regions and emission regions, a first electrode which isformed on each of the emission regions of the substrate, an organiclight-emitting layer which is formed on the first electrode, a secondelectrode which is formed on the organic light-emitting layer and thesubstrate, and a passivation layer which is formed on the secondelectrode, wherein the passivation layer comprises a first passivationlayer which substantially overlaps the organic light-emitting layer anda second passivation layer which does not overlap the organiclight-emitting layer, wherein a refractive index of the firstpassivation layer is higher than a refractive index of the secondpassivation layer.

Another aspect is a method of manufacturing an OLED display, the methodcomprising preparing a first substrate which comprises an organiclight-emitting layer and a second substrate which seals the firstsubstrate, placing filler between the first substrate and the secondsubstrate, bonding the first substrate and the second substrate togetherand forming a first passivation layer which overlaps the organiclight-emitting layer and a second passivation layer which does notoverlap the organic light-emitting layer, wherein a refractive index ofthe first passivation layer is higher than a refractive index of thesecond passivation layer.

Another aspect is a method of manufacturing an OLED display, the methodcomprising preparing a first substrate which comprises an organiclight-emitting layer and a second substrate which seals the firstsubstrate, forming a second passivation layer, which does not overlapthe organic light-emitting layer, on the first substrate, spreadingfiller between the second passivation layer and another secondpassivation layer and bonding the first substrate and the secondsubstrate together and forming a first passivation layer by curing thefiller, wherein a refractive index of the first passivation layer ishigher than a refractive index of the second passivation layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above described and other aspects and features of the describedtechnology will become more apparent by describing in detail exemplaryembodiments thereof with reference to the attached drawings.

FIG. 1 is a block diagram of an OLED display according to an embodiment.

FIG. 2 is a cross-sectional view of a panel taken along the line II-II′of FIG. 1.

FIG. 3 is a cross-sectional view of a first passivation layer and asecond passivation layer according to an embodiment.

FIG. 4 is a plan view of the first passivation layer and the secondpassivation layer shown in FIG. 2.

FIGS. 5 and 6 are cross-sectional views of a first passivation layer anda second passivation layer according to another embodiment.

FIG. 7 is a cross-sectional view of a first passivation layer and asecond passivation layer according to another embodiment.

FIG. 8 is a cross-sectional view of a panel of an OLED display accordingto another embodiment.

FIG. 9 is a cross-sectional view of a panel of an OLED display accordingto another embodiment.

FIG. 10 is a flowchart illustrating a method of manufacturing an OLEDdisplay according to an embodiment.

FIG. 11 is a cross-sectional view illustrating an operation of bonding afirst substrate and a second substrate in the manufacturing method ofFIG. 10.

FIGS. 12 and 13 are cross-sectional views illustrating an operation offorming a first passivation layer and a second passivation layer in themanufacturing method of FIG. 10.

FIG. 14 is a flowchart illustrating a method of manufacturing an OLEDdisplay according to another embodiment.

FIG. 15 is a cross-sectional view illustrating an operation of forming asecond passivation layer in the manufacturing method of FIG. 14.

FIG. 16 is a cross-sectional view illustrating an operation of forming afirst passivation layer in the manufacturing method of FIG. 14.

FIG. 17 is a cross-sectional view illustrating an operation of forming asecond passivation layer in a method of manufacturing an OLED displayaccording to another embodiment.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

OLED displays generally include a thin-film transistor and an OLED foreach of many pixels formed on a substrate and are sealed with a sealingmember such as glass fit, for example. The sealing member can preventpenetration of moisture and foreign matter into each OLED and thin-filmtransistor. In addition, filler is typically interposed between thesealing member and the substrate. The filler can protect the OLED byabsorbing external impact and can cool the OLED by absorbing heatemitted from the OLED. However, the filler can absorb part of the lightemitted by the OLED, thereby reducing the light-emission efficiency ofthe OLED display.

Advantages and features of the described technology and methods ofaccomplishing the same may be understood more readily by reference tothe following detailed description of preferred embodiments and theaccompanying drawings. The described technology may, however, beembodied in many different forms and should not be construed as beinglimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete andwill fully convey the concept of the described technology to thoseskilled in the art, and the described technology will only be defined bythe appended claims. Thus, in some embodiments, well-known structuresand devices are not shown in order not to obscure the description of thedescribed technology with unnecessary detail. Like numbers refer to likeelements throughout. In the drawings, the thickness of layers andregions may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on,” or “connected to” another element or layer, it can bedirectly on or connected to the other element or layer or interveningelements or layers may be present. In contrast, when an element isreferred to as being “directly on” or “directly connected to” anotherelement or layer, there are no intervening elements or layers present.As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Throughout thespecification, the term “connected” includes “electrically connected.”

Spatially relative terms, such as “below,” “beneath,” “lower,” “above,”“upper,” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures.

Hereinafter, embodiments of the described technology will be describedin detail with reference to the attached drawings.

FIG. 1 is a block diagram of an OLED display 10 according to anembodiment of the described technology.

Referring to FIG. 1, the OLED display 10 may include a driving unit 12and a panel 11. The driving unit 12 may include a timing controller Tc,a scan driver Sd, and a data driver Dd. The timing controller Tc, thescan driver Sd and the data driver Dd may be formed as one integratedcircuit (IC) or may respectively be formed as separate ICs.Alternatively, only some of them may be combined into one IC.

The timing controller Tc may receive image data R, G, B and generate ascan driver control signal SCS and a data driver control signal DCSwhich correspond to the received image data R, G, B.

The scan driver Sd may receive the scan driver control signal SCS andgenerate first through n^(th) scan signals S1 through Sn correspondingto the received scan driver control signal SCS. Each of the firstthrough n^(th) scan signals S1 through Sn may have an electric potentialof a scan-on voltage or a scan-off voltage. The first through n^(th)scan signals S1 through Sn may sequentially have the electric potentialof the scan-on voltage. When the first through n^(th) scan signals S1through Sn have the electric potential of the scan-on voltage, firstthrough m^(th) data signals D1 through Dm may be transmitted to aplurality of pixels PX.

The data driver Dd may receive the data driver control signal DCS andgenerate the first through m^(th) data signals D1 through Dmcorresponding to the received data driver control signal DCS. The firstthrough m^(th) data signals D1 through Dm may be generated to besynchronized with the first through n^(th) scan signals S1 through Sn.The first through m^(th) data signals D1 through Dm may includeinformation about the grayscale of an image displayed on the panel 11.

The panel 11 may include pixels PX. The pixels PX may be arranged in asubstantially matrix pattern. However, the arrangement of the pixels PXis not limited to a matrix pattern. The pixels PX may be controlleddifferently and may emit light differently to display an image on thewhole surface of the panel 11. Each of the pixels PX may include anorganic light-emitting layer EL and a thin-film transistor TR. Theorganic light-emitting layer EL may emit light by itself. The thin-filmtransistor TR may drive the organic light-emitting layer EL and controlthe luminance of the organic light-emitting layer EL. The thin-filmtransistor TR may control a pixel PX to receive or not receive a datasignal in response to the scan-on voltage of a scan signal, therebycontrolling the luminance of the organic light-emitting layer EL.

The structure of the panel 11 of the OLED display 10 will now bedescribed in greater detail with reference to FIG. 2. FIG. 2 is across-sectional view of the panel 11 of the OLED display 10, taken alongthe line II-II′ of FIG. 1.

Referring to FIG. 2, the panel 11 includes a substrate S, a firstelectrode 121, the organic light-emitting layer EL, a second electrode122, and a passivation layer f.

The substrate S may be shaped like a substantially flat plate. Thesubstrate S may be formed of an insulating material. In an example, thesubstrate S may be formed of glass, quartz, ceramic or plastic.According to some embodiments, the substrate S may be formed of amaterial that can be easily bent by an external force.

In some embodiments, the substrate S may further include a buffer layerwhich is formed on the substrate S to substantially prevent diffusion ofimpurity ions, substantially prevent penetration of moisture and outsideair, and planarize the surface of the substrate S.

The substrate S may include the pixels PX. Each of the pixels PX mayinclude a non-emission region NF and an emission region EF. That is, thesubstrate S may include a plurality of non-emission regions NF and aplurality of emission regions EF, and the emission regions EF and thenon-emission regions NF may be arranged alternately. Here, each of theemission regions EF may be a region where the organic light-emittinglayer EL is formed and light is emitted from the organic light-emittinglayer EL. Each of the non-emission regions NF may be a region where thethin-film transistor TR driving the organic light-emitting layer EL isformed.

The thin-film transistor TR may include a semiconductor layer 111, agate electrode 112, a source electrode 113, and a drain electrode 114.

The semiconductor layer 111 may be disposed on each of the non-emissionregions NF. The semiconductor layer 111 may be formed of amorphoussilicon or polysilicon. The semiconductor layer 111 may include achannel region 111C, a source region 111S, and a drain region 111D. Thechannel region 111C may be disposed between the source region 111S andthe drain region 111D. The channel region 111C may be overlapped by thegate electrode 112. Depending on a voltage applied to the gate electrode112, the channel region 111C may become conductive or non-conductive,thereby electrically connecting or insulating the source region 111S andthe drain region 111D. A first insulating layer 131 may be formed on thesemiconductor layer 111. The first insulating layer 131 may be formed ofan inorganic material such as SiNx or SiOx, but is not limited thereto.According to some embodiments, the first insulating layer 131 may alsobe formed of an organic material.

The gate electrode 112 may be disposed on the first insulating layer 131to be insulated from the semiconductor layer 111 and overlap the channelregion 111C. The gate electrode 112 may be formed of a conductivematerial. Examples of the conductive material that forms the gateelectrode 112 may include, but is not limited to, a transparentconductive material (such as indium tin oxide (ITO)), titanium (Ti),molybdenum (Mo), aluminum (Al), silver (Ag), copper (Cu) and alloys ofthese materials. A voltage applied to the first gate electrode 112 maycontrol activation of the channel region 111C, and the thin-filmtransistor TR may be turned on or off according to the activation ordeactivation of the channel region 111C.

A second insulating layer 132 may be formed on the gate electrode 112.The second insulating layer 132 may be formed of the same inorganic ororganic material as the first insulating layer 131.

The source electrode 113 and the drain electrode 114 may be disposed onthe second insulating layer 132. The source electrode 113 and the drainelectrode 114 may contact the source region 111S and the drain region111D through first contact holes C1, respectively. In response to theactivation of the channel region 111C, an electric current may flow fromthe source electrode 113 to the drain electrode 114. Then, the drainelectrode 114 may allow the electric current to flow to the firstelectrode 121 through a second contact hole C2. A third insulating layer133 may be formed on the source electrode 113 and the drain electrode114 to insulate and protect the source electrode 113 and the drainelectrode 114. The third insulating layer 133 may be formed of the sameinorganic or organic material as the first insulating layer 131.

The first electrode 121 may be formed on each of the emission regions EFof the substrate S, and the organic light-emitting layer EL may beformed on the first electrode 121. Therefore, respective cross-sectionalareas of the first electrode 121 and the organic light-emitting layer ELmay be substantially equal to a cross-sectional area of each of theemission regions EF. The second electrode 122 may be formed on theorganic light-emitting layer EL and the substrate S. The first electrode121, the organic light-emitting layer EL and the second electrode 122may form an OLED EML. The OLED EML may be a top-emission device whichemits light upward. That is, light emitted from the organiclight-emitting layer EL may proceed in an upward direction D1 of thepanel 11. However, the described technology is not limited thereto.According to some embodiments, the OLED EML may be a bottom-emissiondevice, and light may proceed in an opposite direction to the upwarddirection D1 of the panel 11.

The first electrode 121 may be formed on the third insulating layer 133.The first electrode 121 may be connected to the drain electrode 114 ofthe thin-film transistor TR by the second contact hole C2. The firstelectrode 121 may be an anode of the OLED EML. The first electrode 121may be formed of a reflective conductive material, a transparentconductive material, or a semi-transparent conductive material. Examplesof the reflective conductive material include lithium (Li), calcium(Ca), lithium fluoride/calcium (LiF/Ca), lithium fluoride/aluminum(LiF/Al), Al, Ag, magnesium (Mg), and gold (Au). Examples of thetransparent conductive material include ITO, indium zinc oxide (IZO),zinc oxide (ZnO), and indium oxide (In₂O₃). The semi-transparentconductive material may be a co-deposition material containing one ormore of Mg and Ag or may be one or more of Mg, Ag, Ca, Li, and Al.

The organic light-emitting layer EL may be disposed on the firstelectrode 121. The organic light-emitting layer EL may emit light at abrightness level corresponding to an electric current flowingtherethrough. Specifically, holes and electrons provided to the organiclight-emitting layer EL may combine together to form excitons. When anenergy level of the excitons changes from an excited state to a groundstate, the organic light-emitting layer EL may emit light correspondingto the change in energy levels. The organic light-emitting layer EL ineach of the pixels PX may emit light of one color. Depending on theorganic material that forms the organic light-emitting layer EL, theorganic light-emitting layer EL may emit red light, green light, or bluelight.

The second electrode 122 may be disposed on the organic light-emittinglayer EL. The second electrode 122 may be disposed on the whole surfaceof the panel 11 as illustrated in FIG. 2. However, the describedtechnology is not limited thereto. The second electrode 122 may be acathode of the organic light-emitting layer EL. The second electrode 122may be formed thin using one or more of Mg, Ag, Ca, Li, and Al. Thus,the second electrode 122 may allow light generated from the organiclight-emitting layer EL to travel upward from the organic light-emittinglayer EL.

The passivation layer f may be formed on the second electrode 122. Thepassivation layer f may be transparent filler interposed between asealing member (not shown) and the substrate S. The passivation layer fmay absorb external impact and thus substantially prevent the externalimpact from being delivered to the thin-film transistor TR and theorganic light-emitting layer EL on the substrate S. In addition, thepassivation layer f may suppress internal heat by absorbing and coolingheat generated from the organic light-emitting layer EL. The passivationlayer EL may include a first passivation layer f1 which overlaps theorganic light-emitting layer EL and a second passivation layer f2 whichdoes not overlap the organic light-emitting layer EL. The structures andcharacteristics of the first passivation layer f1 and the secondpassivation layer f2 will now be described in detail with reference toFIGS. 3 and 4.

FIG. 3 is a cross-sectional view of a first passivation layer f1 and asecond passivation layer f2 according to an embodiment of the describedtechnology. FIG. 4 is a plan view of the first passivation layer f1 andthe second passivation layer f2 shown in FIG. 2. That is, FIG. 3 is anenlarged view of a region A, illustrating the relationship between thefirst passivation layer f1 and the second passivation layer f2, and FIG.4 is a plan view of the panel 11 of FIG. 2 viewed from above.

Referring to FIGS. 3 and 4, since the first passivation layer f1substantially overlaps the organic light-emitting layer EL, across-sectional area of the first passivation layer f1 may besubstantially equal to the cross-sectional area of each of the emissionregions EF. If the OLED EML is a top-emission type, the firstpassivation layer f1 may be the path light follows when emitted from theorganic light-emitting layer EL. That is, the light may travel upward inthe panel 11 and pass through the first passivation layer f1 to beemitted to the outside of the panel 11.

Since the second passivation layer f2 does not overlap the organiclight-emitting layer EL, the first passivation layer f1 and the secondpassivation layer f2 may be arranged alternately when viewed in a planeview. In addition, when the panel 11 is viewed from above, the firstpassivation layers f1 may be arranged in a substantially matrix patternin the second passivation layer f2. Since the second passivation layerf2 does not overlap the organic light-emitting layer EL, it is not adirect path for light to travel through. However, part of the emittedlight can be diffused to the second passivation layer f2. That is,portions L1, L2 and L3 of light emitted from the organic light-emittinglayer EL may not proceed directly upward in the panel 11 but may proceedtoward the second passivation layer f2 after passing through the firstpassivation layer f1.

Here, the first passivation layer f1 may have a higher refractive indexthan the second passivation layer f2. The first passivation layer f1 mayinclude a material having a high refractive index of about 1.6 or more.The high refractive material may be spread over the whole surface of thefirst passivation layer f1 so as to increase the overall refractiveindex of the first passivation layer f1 or may be provided at a boundarysurface with the second passivation layer f2 so as to increase therefractive index of the first passivation layer f1 at the boundarysurface. The second passivation layer f2 may include a material having arefractive index of less than about 1.6. The material having therefractive index of less than about 1.6 may be spread over the wholesurface of the second passivation layer f2 so as to decrease the overallrefractive index of the second passivation layer f2 or may be providedat the boundary surface with the first passivation layer f1 so as todecrease the refractive index of the second passivation layer f2 at theboundary surface.

The material having the high refractive index of about 1.6 or more maybe high refractive curable polysilicon such as polydiaryl siloxane,methyltrimethoxysilane or tetramethoxysilane. The material having therefractive index of less than about 1.6 may be a low refractiveultraviolet-curable acrylate polymer such as ethylhexyl acrylate,pentafluoropropyl acrylate, poly(ethylene glycol) dimethacrylate orethylene glycol dimethacrylate.

When light L1, L2 or L3 moves from a high refractive medium to a lowrefractive medium, it may be refracted to the low refractive medium ormay be reflected to the high refractive medium according to thedifference between refractive indices of the high and low refractivemediums. Therefore, the light L1, L2 or L3 travelling from the firstpassivation layer f1 having a high refractive index to the secondpassivation layer f2 having a low refractive index may be refracted tothe second passivation layer f2 or may be reflected to the firstpassivation layer f1. The path of the light L1, L2 or L3 may bedetermined by an incidence angle θ1, θ2 or θ3 of the light L1, L2 or L3incident upon a boundary surface I between the first passivation layerf1 and the second passivation layer f2. In an example, when theincidence angle θ1 is smaller than a critical angle θc, a portion of thelight L1 may be reflected at the boundary surface I, but another portionof the light L1 may proceed to the second passivation layer f2. Here,the critical angle θc may be determined by the refractive indices of thefirst passivation layer f1 and the second passivation layer f2. When theincidence angle θ2 is equal to the critical angle θc, the light L2 maynot be reflected nor refracted but may proceed along the boundarysurface I. When the incidence angle θ3 is greater than the criticalangle θc, the incident light L3 may not be refracted to the secondpassivation layer f2 but may be totally reflected at the boundarysurface I to proceed back into the first passivation layer f1. Here, asthe amount of totally reflected light increases, more light can beconcentrated to the first passivation layer f1.

The above-described structural or optical characteristics of thepassivation layer f enable the passivation layer f to concentrate lightin the first passivation layer f1 which corresponds to each of theemission regions EF. Therefore, the passivation layer f can provide animproved light-emission effect. Furthermore, the passivation layer f cansubstantially prevent color mixture between the pixels PX by minimizingthe diffusion of light to the second passivation layer f2.

FIGS. 5 and 6 are cross-sectional views of a first passivation layer f1and a second passivation layer f2 according to another embodiment.

Referring to FIGS. 5 and 6, a cross-sectional area UW of a top surfaceof the first passivation layer f1 may be greater than a cross-sectionalarea BW of a bottom surface of the first passivation layer f1. Here, thebottom surface may be a surface of the first passivation layer f1 whichcontacts the second electrode 122, and the top surface may be a surfaceof the first passivation layer f1 which is exposed to the outside of theOLED display 10. The cross-sectional area of the first passivation layerf1 may increase from the bottom surface of the first passivation layerf1 toward the top surface thereof. That is, referring to FIG. 5, aboundary surface I′ between the first passivation layer f1 and thesecond passivation layer f2 may be an inclined surface with apredetermined slope. Alternatively, referring to FIG. 6, the boundarysurface I′ may be a curved inclined surface whose slope increases fromthe bottom surface of the first passivation layer f1 toward the topsurface thereof. That is, a cross-section of the first passivation layerf1 may have an overhang structure with a reverse inclined surface and beshaped like a reverse trapezoid.

The boundary surface I′ may cause more light rays to have greaterincidence angles than a critical angle, as compared with the boundarysurface I of FIG. 4. That is, since the boundary surface I′ is inclined,light L3 or L4 having a greater incidence angle θ3 or θ4 may enter theboundary surface I′. Therefore, the light L3 or L4 may be totallyreflected to be concentrated in the first passivation layer f1 whichcorresponds to each of the emission regions EF. That is, a passivationlayer f according to the current embodiment can provide improvedlight-emission efficiency by maximizing the amount of light that istotally reflected in the first passivation layer f1 and minimizing theamount of light that is sent to the second passivation layer f2.Furthermore, the passivation layer f can substantially prevent colormixture between pixels.

FIG. 7 is a cross-sectional view of a first passivation layer f1 and asecond passivation layer f2 according to another embodiment.

Referring to FIG. 7, the OLED display 10 may further include a pixeldefining layer PDL. The pixel defining layer PDL may be disposed betweenthe organic light-emitting layers EL. The pixel defining layer PDL maybe formed of the same organic or inorganic material as the firstinsulating layer 131. The pixel defining layer PDL may be formed on aregion of the third insulating layer 133 which corresponds to each ofthe non-emission regions NF, thereby defining each of the emissionregions EF.

The pixel defining layer PDL may be formed at an angle to the organiclight-emitting layer EL and may be stacked to a height h2 greater than aheight h1 to which the organic light-emitting layer EL is stacked. Thatis, the pixel defining layer PDL may slope at a predetermined angle θpto the organic light-emitting layer EL. A portion of light emitted fromthe organic light-emitting layer EL may proceed to a boundary surface Ialong the slope of the pixel defining layer PDL. Here, an incidenceangle of the portion of the light at the boundary surface I may be equalto the angle θp. The angle θp may be greater than a critical angle θcdetermined by refractive indices of the first passivation layer f1 andthe second passivation layer f2. Therefore, the incidence angle θp ofthe portion of the light at the boundary surface I may be greater thanthe critical angle θc, and the portion of the light may be totallyreflected to the first passivation layer f1. That is, the pixel defininglayer PDL may concentrate more light to the first passivation layer f1by guiding emitted light to have an incidence angle greater than thecritical angle θc. This can further improve the light-emissionefficiency of the organic light-emitting layer EL.

FIG. 8 is a cross-sectional view of a panel 31 of an OLED displayaccording to another embodiment.

Referring to FIG. 8, the panel 31 of the OLED display may furtherinclude a color filter CF formed on a passivation layer f. The colorfilter CF may include a filter layer C formed on a first passivationlayer f1 and a black matrix BM formed on a second passivation layer f2.The filter layer C may correspond to each of emission regions. EF, andthe black matrix BM may correspond to each of non-emission regions NF.

The filter layer C may convert a color of light that passes through thefilter layer C into a color of the filter layer C. The light may bewhite light w. The filter layer C may have any one of red, green andblue colors which are three primary colors of light. However, thedescribed technology is not limited thereto. In some embodiments, thefilter layer C may have any one of cyan, magenta and yellow which arecomplementary colors of red, green and blue. In some embodiments, thecolor filter CF may further include a transparent filter layer C thatallows the white light w to pass therethrough without a change in orderto improve its ability to express bright colors.

The black matrix BM may block light incident to the second passivationlayer f2 from being emitted to the outside of the panel 31. That is, theblack matrix BM can substantially prevent color mixture between pixelsPX and define the filter layer C.

An organic light-emitting layer EL may emit the white light w upward,and the white light w may be converted into the color of the filterlayer C as it passes through the filter layer C. As described above, aportion of emitted light may be totally reflected to the firstpassivation layer f1 at a boundary surface between the first passivationlayer f1 and the second passivation layer f2. Therefore, it is possibleto substantially prevent the diffusion of the portion of the light andconcentrate the portion of the light to the first passivation f1,thereby improving light-emission efficiency. In addition, anotherportion of the emitted light may be refracted at the boundary surfacebetween the first passivation layer f1 and the second passivation layerf2 to the black matrix BM formed on the second passivation layer f2.Therefore, the OLED display can substantially prevent color mixturebetween the pixels PX more effectively.

Other elements of the OLED display which are substantially the same asthose of the OLED display 10 described above with reference to FIGS. 1through 7 are identified by the same names and will not be described.

FIG. 9 is a cross-sectional view of a panel 41 of an OLED displayaccording to another embodiment.

Referring to FIG. 9, the panel 41 of the OLED display may furtherinclude a filter layer C formed on a first passivation layer f1. Thefilter layer C is substantially the same as the filter layer C of theOLED display of FIG. 8, and thus a description thereof will be omitted.

An organic light-emitting layer EL may emit white light w upward, andthe white light w may be converted into a color of the filter layer C asit passes through the filter layer C.

A cross-sectional area of the first passivation layer f1 may increasefrom a bottom surface of the first passivation layer f1 toward a topsurface thereof, and a boundary surface of the first passivation layerf1 with a second passivation layer f2 may be inclined. Here, thecross-sectional area of the bottom surface of the first passivationlayer f1 may be substantially equal to a cross-sectional area of each ofemission regions EF and a cross-sectional area of the organiclight-emitting layer EL.

The inclined boundary surface may provide an incidence angle that causesmost light to be totally reflected to the first passivation layer f1 andmay minimize the amount of light sent to the second passivation layerf2. Therefore, since light can be concentrated to the first passivationlayer f1, light-emission efficiency can be increased. In addition, sincemost of the light sent to the second passivation layer f2 can beblocked, color mixture between pixels PX can be substantially prevented.That is, even without a black matrix BM, the second passivation layer f2stacked to a height substantially equal to a top surface of the filterlayer C can define the filter layer C.

The OLED display according to the current embodiment can increaselight-emission efficiency by concentrating emitted light to the firstpassivation layer f1 and can increase an aperture ratio by not includingthe black matrix BM.

Other elements of the OLED display which are substantially the same asthose of the OLED display 10 described above with reference to FIGS. 1through 7 are identified by the same names and will not be described.

A method of manufacturing the above OLED displays will hereinafter bedescribed in detail.

FIG. 10 is a flowchart illustrating a method of manufacturing an OLEDdisplay according to an embodiment.

Referring to FIG. 10, the method of manufacturing the OLED displayincludes preparing a first substrate and a second substrate (operationS110), bonding the first substrate and the second substrate together(operation S120), and forming a first passivation layer and a secondpassivation layer (operation S130).

First, a first substrate S1 and a second substrate S2 are prepared(operation S110).

The first substrate S1 may be formed of an insulating material. In anexample, the first substrate S1 may be formed of glass, quartz, ceramicor plastic. The first substrate S1 may support other elements placedthereon. The first substrate S1 may include non-emission regions NF andemission regions EF. In addition, the first substrate S1 may include athin-film transistor TR formed on each of the non-emission regions NFand an OLED EML formed on each of the emission regions EF.

In the preparing of the first substrate S1, the thin-film transistor TRmay be formed on each of the non-emission regions NF, and an organiclight-emitting layer EL may be formed on each of the emission regionsEF. The thin-film transistor TR may include a semiconductor layer 111, agate electrode 112, a drain electrode 114 and a source electrode 113,and the OLED EML may include a first electrode 121, the organiclight-emitting layer EL, and a second electrode 122. Here, the organiclight-emitting layer EL may correspond to each of the emission regionsEF. That is, a cross-sectional area of the organic light-emitting layerEL may be substantially equal to a cross-sectional area of each of theemission regions EF.

The above elements may be formed by a photolithography process using aphotomask. The photolithography process may include a series ofprocesses including exposing using an exposure device (not shown),developing, etching, and stripping or ashing.

In some embodiments, the preparing of the first substrate S1 may furtherinclude forming a buffer layer on the first substrate S1 tosubstantially prevent diffusion of impurity ions, substantially preventpenetration of moisture and outside air, and planarize the surface ofthe substrate S1.

The second substrate S2 may be an encapsulation substrate for sealingthe first substrate S1. That is, the second substrate S1 maysubstantially prevent penetration of external impurities and moistureinto the first substrate S1. The second substrate S2 may be a glasssubstrate or a plastic substrate formed of various plastic materialssuch as acrylic. In a top-emission OLED display, the second substrate S2may be an electrically insulating material having high transmittance forlight generated from the organic light-emitting layer EL. In an example,the second substrate S2 may include transparent glass (such as alkaliglass or alkali-free gas), transparent ceramics (such as polyethyleneterephthalate, polycarbonate, polyether sulfone, polyvinyl fluoride(PVF), polyacrylate or zirconia), or quartz.

Next, the first substrate S1 and the second substrate S2 are bondedtogether (operation S120). This will be described in detail withreference to FIG. 11.

FIG. 11 is a cross-sectional view illustrating the bonding of the firstsubstrate and the second substrate (operation S120) in the manufacturingmethod of FIG. 10.

Referring to FIG. 11, filler f may be placed between the first substrateS1 and the second substrate S2, and then the first substrate S1 and thesecond substrate S2 may be bonded together. The first substrate S1 andthe second substrate S2 may be bonded together by an encapsulant (notshown). The encapsulant (not shown) may be placed between the firstsubstrate S1 and the second substrate S2. The encapsulant (not shown)may be fit which is gel-state glass obtained by adding organic matter topowder-state glass. The encapsulant may be cured with laser irradiationto solidify the encapsulant, thereby bonding the first substrate S1 andthe second substrate S2 together.

The filler f may be placed in a space formed by the first substrate S1,the second substrate S2 and the encapsulant. Since the filler f fillsthe space as it is cured, it can protect devices formed on the firstsubstrate S1 from external impact. The filler f may include a highrefractive material H and a low refractive material L. That is, thefiller f contains a mixture of the high refractive material H and thelow refractive material L which are movable. The high refractivematerial H may include high refractive curable monomers such aspolydiarylsiloxane, methyltrimethoxysilane or tetramethoxysilane. Thelow refractive material L may include ultraviolet-curable monomers suchas ethylhexyl acrylate, pentafluoropropyl acrylate, poly(ethyleneglycol) dimethacrylate, or ethylene glycol dimethacrylate. The highrefractive material H may be cured to form a first passivation layer f1,and the low refractive material L may be cured to form a secondpassivation layer f2. The formation of the first passivation layer f1and the second passivation layer f2 will be described below.

Finally, the first passivation layer f1 and the second passivation layerf2 are formed (operation S130). This will be described with reference toFIGS. 12 and 13.

FIGS. 12 and 13 are cross-sectional views illustrating the forming ofthe first passivation layer f1 and the second passivation layer f2(operation S130) in the manufacturing method of FIG. 10. The forming ofthe first passivation layer f1 and the second passivation layer f2 maybe achieved by selective ultraviolet irradiation. Referring to FIG. 12,a mask may include light-transmitting portions Mb which transmit light100% and light-blocking portions Ma which block light 100%, that is,have a light transmittance of 0%. A cross-sectional area of each of thelight-transmitting portions Mb may be substantially equal to thecross-sectional area of each of the non-emission regions NF of the firstsubstrate S1, and a cross-sectional area of each of the light-blockingportions Ma may be substantially equal to the cross-sectional area ofeach of the emission regions EF of the first substrate S1. Therefore,the cross-sectional area of each of the light-blocking portions Ma maybe substantially equal to the cross-sectional area of the organiclight-emitting layer EL. The mask M may be placed over the OLED displaysuch that regions with substantially equal cross-sectional areas arealigned with each other.

Ultraviolet light UV may be irradiated toward the OLED display fromabove the mask M. The ultraviolet light UV may transmit through thelight-transmitting portions Mb and the transparent second substrate S2to reach the filler f. Accordingly, the ultraviolet light UV may beirradiated only to ultraviolet irradiation regions U1 of the filler f.The ultraviolet irradiation regions U1 of the filler f may correspondnot only to the light-transmitting portions Mb but also to thenon-emission regions NF. Low refractive ultraviolet-curable monomers ofthe ultraviolet irradiation regions U1 may polymerize to form a lowrefractive ultraviolet-curable polymer. This polymerization may occurserially, and the high refractive material H may move to ultravioletnon-irradiation regions U2 as the above low refractive polymer occupiesmost of the ultraviolet irradiation regions U1. In addition, lowrefractive ultraviolet-curable monomers of the ultravioletnon-irradiation regions U2 may move to the ultraviolet irradiationregions U1 so as to participate in polymerization. Each of theultraviolet irradiation regions U1 may become the second passivationlayer f2 which is formed of a polymer of the low refractive material L.After the formation of the second passivation layer f2, each of theultraviolet non-irradiation regions U2 may become the first passivationlayer f1, which is formed of a high refractive material, throughpolymerization between the high refractive materials H. The firstpassivation layer f1 may be formed on each of the emission regions EFand substantially overlap the organic light-emitting layer EL.

That is, selective ultraviolet irradiation may result in the formationof the first passivation layer f1 which substantially overlaps theorganic light-emitting layer EL and the second passivation layer f2which does not overlap the organic light-emitting layer EL, asillustrated in FIG. 13. In the manufacturing method according to thecurrent embodiment, the second passivation layer f2 is formed before thefirst passivation layer f1. However, the described technology is notlimited thereto. In some embodiments, the first passivation layer f1 maybe formed by selective ultraviolet irradiation, and then the secondpassivation layer f2 may be formed between the first passivation layersf1. In this case, the high refractive material H may be cured first.

The first passivation layer f1 may include a material having arefractive index of about 1.6 or more, and the second passivation layerf2 may include a material having a refractive index of less than about1.6. That is, the refractive index of the first passivation layer f1 maybe higher than the refractive index of the second passivation layer f2.Accordingly, since light emitted from the organic light-emitting layerEL can be concentrated to the emission regions EF as described above, itis possible to enhance light-emission efficiency and substantiallyprevent color mixture between pixels PX.

In some embodiments, the preparing of the second substrate S2 (operationS110) may further include forming a color filter CF on the secondsubstrate S2. Here, the color filter CF may include a filter layer Cwhich corresponds to each of the emission regions EF of the firstsubstrate S1 and a black matrix BM which corresponds to each of thenon-emission regions NF to define the filter layer C. In the forming ofthe first passivation layer f1 and the second passivation layer f2(operation S130), selective ultraviolet irradiation can be performedusing the color filter CF, not using a mask. That is, selectiveultraviolet irradiation can be performed using the black matrix BM aseach of the light-blocking portions Ma and the filter layer C as each ofthe light-transmitting portions Mb. In this case, the high refractivematerial H may be cured first to form the first passivation layer f1,and the low refractive material L may form the second passivation layerf2 between the first passivation layers f1. Since a cross-sectional areaof the filter layer C is substantially equal to the cross-sectional areaof each of the emission regions EF and the cross-sectional area of theorganic light-emitting layer EL, the first passivation layer f1 maysubstantially overlap the organic light-emitting layer EL.

In some embodiments, the preparing of the second substrate S2 (operationS110) may further include forming a filter layer C on the secondsubstrate S2 to correspond to each of the emission regions EF of thefirst substrate S1. In addition, the forming of the second passivationlayer f2 (operation S130) may further include forming the secondpassivation layer f2 to a height equal to a top surface of the filterlayer C such that the filter layer C can be defined by the secondpassivation layer f2.

FIG. 14 is a flowchart illustrating a method of manufacturing an OLEDdisplay according to another embodiment.

Referring to FIG. 14, the method of manufacturing the OLED displayincludes preparing a first substrate and a second substrate (operationS210), forming a second passivation layer (operation S220), bonding thefirst substrate and the second substrate together (operation S230), andforming a first passivation layer (operation S240).

First, the first substrate and the second substrate are prepared(operation S210). The preparing of the first substrate and the secondsubstrate (operation S210) is substantially the same as the preparing ofthe first substrate and the second substrate (operation S110) in themanufacturing method according to the previous embodiment, and thus adetailed description thereof will be omitted.

Next, the second passivation layer is formed (operation S220). This willbe described in detail with reference to FIG. 15.

FIG. 15 is a cross-sectional view illustrating the forming of the secondpassivation layer (operation S220) in the manufacturing method of FIG.14.

A second passivation layer f2 may be formed only on each of non-emissionregions NF of a first substrate S1. The second passivation layer f2 maybe formed on each of the non-emission regions NF by a lithographyprocess using photoresist or a laser ablation process using laser beamirradiation. That is, the second passivation layer f2 may be spread overthe whole surface of the first substrate S1 and then cured. In thisstate, regions of the second passivation layer f2 which correspond tothe non-emission regions NF may be left unremoved, and the other regionsof the second passivation layer f2 may be removed by anisotropicetching. Here, since the second passivation layer f2 is formed on eachof the non-emission regions NF, it may not overlap an organiclight-emitting layer EL formed on each of emission regions EF.

The second passivation layer f2 may include a material having arefractive index of less than about 1.6. The material having therefractive index of less than about 1.6 may be a low refractiveultraviolet-curable polymer such as ethylhexyl acrylate,pentafluoropropyl acrylate, poly(ethylene glycol) dimethacrylate orethylene glycol dimethacrylate.

In the current embodiment, the second passivation layer f2 is formed onthe first substrate S1 before a first passivation layer f1. However, thedescribed technology is not limited thereto. In some embodiments, thefirst passivation layer f1 may be formed on the first substrate S1before the second passivation layer f2, or the first passivation layerf1 and the second passivation layer f2 may be filmed on a secondsubstrate S2.

Next, the first substrate and the second substrate are bonded together(operation S230).

Filler may be spread on each of the emission regions EF of the firstsubstrate S1. That is, the filler may be spread between the secondpassivation layers f2. The filler may include monomers of a highrefractive material.

The first substrate S1 and the second substrate S2 may be bondedtogether with an encapsulant (not shown). The encapsulant (not shown)may be placed between the first substrate S1 and the second substrateS2. The encapsulant (not shown) may be fit which is gel-state glassobtained by adding organic matter to powder-state glass. The encapsulantmay be cured with laser irradiation to solidify the encapsulant, therebybonding the first substrate S1 and the second substrate S2 together.

Finally, the first passivation layer f1 is formed (operation S240). Thiswill be described with reference to FIG. 16.

FIG. 16 is a cross-sectional view illustrating the forming of the firstpassivation layer (operation S240) in the manufacturing method of FIG.14.

Referring to FIG. 16, the filler spread on each of the emission regionsEF of the first substrate S1 may be cured to form the first passivationlayer f1. That is, monomers of a high refractive material contained inthe filler may be cured into a polymer, and the first passivation layerf1 including the high refractive polymer may be formed. The highrefractive polymer may be a material having a refractive index of about1.6 or more. The material having the high refractive index of about 1.6or more may be high refractive curable polysilicon such as polydiarylsiloxane, methyltrimethoxysilane or tetramethoxysilane.

The first passivation layer 11 may be formed on each of the emissionregions EF, and the second passivation layer f2 may be formed on each ofthe non-emission regions NF. The refractive index of the firstpassivation layer f1 may be higher than the refractive index of thesecond passivation layer f2. Accordingly, since light emitted from theorganic light-emitting layer EL can be concentrated in the emissionregions EF as described above, it is possible to enhance light-emissionefficiency and substantially prevent color mixture between pixels.

In some embodiments, the preparing of the second substrate S2 (operationS210) may further include forming a color filter CF on the secondsubstrate S2. Here, the color filter CF may include a filter layer Cwhich corresponds to each of the emission regions EF of the firstsubstrate S1 and a black matrix BM which corresponds to each of thenon-emission regions NF to define the filter layer C.

In some embodiments, the preparing of the second substrate S2 (operationS210) may further include forming a filter layer C on the secondsubstrate S2 to correspond to each of the emission regions EF of thefirst substrate S1. In addition, the forming of the second passivationlayer f2 (operation S220) may further include forming the secondpassivation layer f2 to a height substantially equal to a top surface ofthe filter layer C such that the filter layer C can be defined by thesecond passivation layer f2.

FIG. 17 is a cross-sectional view illustrating the forming of the secondpassivation layer in a method of manufacturing an OLED display accordingto another embodiment.

The forming of the second passivation layer in the manufacturing methodaccording to the current embodiment may further include removing aregion of a second passivation layer f2 to form an inclined boundarysurface between a first passivation layer f1 and the second passivationlayer f2 after forming the second passivation layer f2 to correspond toeach of non-emission regions NF. The region of the second passivationlayer f2 may be removed by, e.g., isotropic etching.

A cross-sectional area BW of a bottom surface of the second passivationlayer f2 may be greater than a cross-sectional area UW of a top surfaceof the second passivation layer f2. Here, the bottom surface may be asurface of the second passivation layer f2 which contacts a firstsubstrate S1. Therefore, a cross-sectional area of the secondpassivation layer f2 may decrease from the bottom surface of the secondpassivation layer f2 toward the top surface thereof. The inclinedboundary surface may cause more light to have an incidence angle greaterthan a critical angle, compared with a vertical boundary surface. Thatis, light having an incidence angle greater than a critical angle θc mayenter the boundary surface and then be totally reflected to the firstpassivation layer f1 which corresponds to each of emission regions EF.Accordingly, the amount of light that is sent to the second passivationlayer f2 can be minimized, and more light can be concentrated to theemission regions EF. This can further improve light-emission efficiency.

According to some embodiments, at least one of the following advantagesmay be provided.

Light-emission efficiency of an OLED display can be improved.

In addition, it is possible to substantially prevent color mixturebetween pixels.

However, the effects of the described technology are not restricted tothose set forth herein. The above and other effects of the describedtechnology will become more apparent to one of ordinary skill in the artto which the described technology pertains by referencing theaccompanying claims.

While the described technology has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the described technology as defined by the following claims. It istherefore desired that the described embodiments be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than the foregoing description to indicatethe scope of the invention.

What is claimed is:
 1. An organic light-emitting diode (OLED) displaycomprising: a substrate comprising non-emission regions and emissionregions; a first electrode formed over each of the emission regions; afirst organic light-emitting layer formed over the first electrode; asecond electrode formed over the first organic light-emitting layer andthe substrate; and first and second passivation layers formed over thesecond electrode and having first and second refractive indexes,respectively, wherein the first refractive index is greater than thesecond refractive index, wherein the first passivation layersubstantially overlaps the first organic light-emitting layer and thesecond passivation layer does not overlap the first organiclight-emitting layer.
 2. The OLED display of claim 1, wherein the firstrefractive index is greater than about 1.6, and wherein the secondrefractive index is less than about 1.6.
 3. The OLED display of claim 2,wherein the first passivation layer is formed at least of a highrefractive curable polysilicon, and wherein the second passivation layeris formed at least of a low refractive ultraviolet-curable polymer. 4.The OLED display of claim 1, further comprising a pixel defining layerformed between the first organic light-emitting layer and a secondorganic light-emitting layer, wherein the pixel defining layer forms anangle with respect to the first organic light-emitting layer and isconfigured to guide light emitted from the first organic light-emittinglayer along a slope thereof.
 5. The OLED display of claim 1, wherein across-sectional area of a top surface of the first passivation layer isgreater than a cross-sectional area of a bottom surface of the firstpassivation layer.
 6. The OLED display of claim 5, wherein across-sectional area of the first passivation layer increases from thebottom surface toward the top surface.
 7. The OLED display of claim 1,wherein the first organic light-emitting layer is configured to emitwhite light, wherein the OLED display further comprises a color filterformed over the first and second passivation layers, and wherein thecolor filter comprises a filter layer formed over the first passivationlayer and a black matrix formed over the second passivation layer todefine the filter layer.
 8. The OLED display of claim 1, wherein thefirst organic light-emitting layer is configured to emit white light,wherein the OLED display further comprises a filter layer formed overthe first passivation layer, wherein a cross-sectional area of the firstpassivation layer increases from a bottom surface of the firstpassivation layer toward a top surface thereof, and wherein the secondpassivation layer is stacked to a height substantially equal to a topsurface of the filter layer so as to define the filter layer.
 9. Amethod of manufacturing an organic light-emitting diode (OLED) display,the method comprising: providing a first substrate comprising an organiclight-emitting layer; providing a second substrate which substantiallyseals the first substrate; placing filler between the first and secondsubstrates; bonding the first and second substrates; and forming i) afirst passivation layer to substantially overlap the organiclight-emitting layer and ii) a second passivation layer, wherein thesecond passivation layer does not overlap the organic light-emittinglayer, wherein the first and second passivation layers have first andsecond refractive indexes, respectively, and wherein the firstrefractive index is greater than the second refractive index.
 10. Themethod of claim 9, wherein the filler comprises a high refractivematerial and a low refractive material, and the forming comprises i)curing the low refractive material with ultraviolet radiation to formthe second passivation layer, and ii) curing the high refractivematerial between the second passivation layer and another secondpassivation layer to form the first passivation layer.
 11. The method ofclaim 10, wherein the first refractive index is greater than about 1.6,and wherein the second refractive index is less than about 1.6.
 12. Themethod of claim 9, wherein the providing of the second substratecomprises forming a color filter over the second substrate, wherein thecolor filter comprises a filter layer corresponding to the firstpassivation layer and a black matrix corresponding to the secondpassivation layer to define the filter layer.
 13. The method of claim 9,wherein the providing of the second substrate comprises forming a filterlayer over the second substrate to correspond to the first passivationlayer, and wherein the filter layer is defined by the second passivationlayer.
 14. A method of manufacturing an organic light-emitting diode(OLED) display, the method comprising: providing a first substratecomprising an organic light-emitting layer; providing a second substrateto substantially seal the first substrate; forming a second passivationlayer over the first substrate, wherein the second passivation layerdoes not overlap the organic light-emitting layer, wherein the first andsecond passivation layers have first and second refractive indexes,respectively, and wherein the first refractive index is greater than thesecond refractive index; placing filler between the second passivationlayer and another second passivation layer and bonding the first andsecond substrates; and curing the filler to form a first passivationlayer.
 15. The method of claim 14, wherein the first refractive index isgreater than about 1.6, and wherein the second refractive index is lessthan about 1.6.
 16. The method of claim 15, wherein the firstpassivation layer is formed at least of a high refractive curablepolysilicon, and wherein the second passivation layer is formed at leastof a low refractive ultraviolet-curable polymer.
 17. The method of claim14, wherein a cross-sectional area of a bottom surface of the secondpassivation layer is greater than a cross-sectional area of a topsurface of the second passivation layer.
 18. The method of claim 17,wherein a cross-sectional area of the second passivation layer decreasesfrom the bottom surface toward the top surface.
 19. The method of claim14, wherein the providing of the second substrate comprises forming acolor filter over the second substrate, and wherein the color filtercomprises a filter layer corresponding to the first passivation layerand a black matrix corresponding to the second passivation layer todefine the filter layer.
 20. The method of claim 14, wherein theproviding of the second substrate comprises forming a filter layer overthe second substrate to correspond to the first passivation layer, andwherein the filter layer is defined by the second passivation layer.